Last Revision — April 19, 2022
2 Min Read
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Bloaters
Data
Between Classes
- Type Embedded In Name (co-exist)
- Obscured Intent (causes)
- Lazy Element (antagonistic)
Martin Fowler in book (1999): "Refactoring: Improving the Design of Existing Code"
Whenever a variable that is just a simple string, or an int simulates being a more abstract concept, which could be an object, we encounter a Primitive Obsession code smell. This lack of abstraction quickly becomes a problem whenever there is the need for any additional logic, and also because these variables easily spread wide and far in the codebase. This alleged verbal abstraction is just a "supposed" object, but it should have a real object instead.
Possibly a missing class to represent the concept in the first place. Mäntylä gives an example of representing money as primitive rather than creating a separate class [1], and so does Fowler, who states that many programmers are reluctant to create their own fundamental types. [2]. Higher-level abstraction knowledge is needed to clarify or simplify the code. [3
The type does not correspond to a variable's value (i.e., phone number as a string).
These primitives often go in groups, and there’s a lack of written relations between them, and nothing protects them from external manipulation.
birthday_date: str = "1998-03-04"
name_day_date: str = "2021-03-20"@dataclass(frozen=True)
class Date:
year: int
month: int
day: int
def __str__(self):
return f"{self.year}-{self.month}-{self.day}"
birthday: Date = Date(1998, 03, 04)
name_day: Date = Date(2021, 03, 20)Note: the above solution is a technical solution example. Practically it is a Clever Code code smell - in Python there is built-in datetime.